Implantable electrical stimulators may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. An implantable medical device may deliver electrical stimulation therapy via leads that include electrodes located proximate to the spinal cord, pelvic nerves, stomach, peripheral nerves, or within the brain of a patient. In general, the implantable medical device delivers electrical stimulation therapy in the form of electrical pulses or another electrical waveform.
A clinician selects values for a number of programmable parameters in order to define the electrical stimulation therapy to be delivered to a patient. For example, the clinician selects an amplitude, which may be a current or voltage amplitude, and, when electrical stimulation is delivered in the form of pulses, a pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient. The clinician may also select particular electrodes within an electrode set to be used as an electrode combination to deliver the electrical stimulation and the polarities of the selected electrodes. A set of parameter values may be referred to as a program in the sense that they drive the electrical stimulation therapy to be delivered to the patient.
Electrical stimulation may be delivered via electrodes carried by one, two or more implantable leads, each of which may include multiple electrodes. Electrical stimulation may be delivered via various combinations of electrodes, including electrodes on a single lead, or electrodes on different leads. For example, one program may specify a combination of relatively proximal electrodes while another program may specify a combination of more distal electrodes. In addition, some programs may include greater or lesser numbers of electrodes, greater or lesser distances between electrodes, or varied positions of cathodes and anodes. In this manner, electrical stimulation can be shaped and targeted relative to nerves, muscle or other tissue or anatomical structures to enhance therapeutic efficacy.